Read/Write Vixie compatible crontab files

Config::Crontab has a simple, object-oriented syntax. Crontab files are
broken into "blocks" (paragraphs, each separated by two or more
newlines); the Block is the basic unit of a Config::Crontab object.

You can re-order entire blocks within a crontab file, re-order lines
within blocks (there are three types of lines: comments, environment
settings, and crontab commands or events), remove blocks or lines
within blocks, add new blocks or lines within blocks, etc. See the
Config::Crontab manpage for full details.